Event · M31
Defence of Ryza in the Horus Heresy
The Defence of Ryza in the Horus Heresy is the recorded ordeal of Ryza, second among the Forge Worlds, during the early 31st-millennium civil war. Ryza is known to the wider Imperium as the plasma forge, its manufactories given over chiefly to the production of plasma weaponry, and its allegiance in this period is remembered through its long association with the Executioners and the Stormblades. The working map of 40k Orrery places Ryza in Segmentum Ultima, just east of Terra, though some older armour books instead locate it within Segmentum Solar; the discrepancy reflects differing editorial traditions rather than any settled contradiction in the world’s own history. At the close of the Great Crusade, Ryza ranked second only to Mars among the Forge Worlds and stood as one of the foremost centres of weapons manufacture in the Imperium, a status that made it a significant asset — and, by extension, a significant target — once the Horus Heresy divided the Mechanicum against itself. Its priesthood is recorded as treating every battle fought on or over the world as an opportunity to field-test new weapons patterns, a practice that predates the Heresy and has remained the defining characteristic of Ryzan military culture since. No surviving account sets out the individual engagements of the defence itself: neither the identities of the attacking forces nor the course of the fighting are recorded in the material available to this encyclopedia, and this gap is noted here rather than filled with invented detail. What is attested is the cost the Heresy exacted from Ryza, a cost bound directly to its rank as a weapons-producing world of the first importance — the same standing that made its forges worth fighting over made any disruption to them correspondingly severe. In the millennia since, Ryza’s dune-covered surface has been ravaged twice more by Ork Waaaghs and once by a daemonic invasion, later trials that the world’s chroniclers set alongside the Heresy-era defence as recurring proof of its endurance. Through each of these ordeals, Ryza’s identity has remained constant: a plasma forge world of the Mechanicum, subordinate in rank only to Mars, whose priesthood continues to test its weapons in the fire of battle rather than in the forge alone.
See where Defence of Ryza in the Horus Heresy occurred on the galactic map during the Horus Heresy.